Studies designed to develop specific diagnostic assays of atrial natriuretic factor and its metabolites are described. Such assays are currently not available, but are required for a complete understanding of atrial natriuretic factor in the regulation of blood pressure. The proposed studies involve the preparation and use of monoclonal antibodies to defined regions of the peptide. The radio and flourimetric assays so developed can be utilized to a) study the excretion, fate and metabolism of ANF and b) serve as diagnostic tools to explore likely correlations between characteristic ANF levels and certain cardiovascular disorders. The latter applicaiton could have tremendous clinical significance.